""" 自定义分页组件 :使用方法
在视图函数中：
def pretty_list(request):
    # 1. 根据自己得情况去筛选数据
    queryset = models.PrettyNum.objects.all()
    # 2. 实列化分页对象
    page_object = Pagination(request, queryset)

    context = {
        "queryset": page_object.page_queryset,  # 分完页数据
        "page_string": page_object.html()       # 生成页码
    }

    return render(request, 'pretty_list.html', context)
在HTML页面中
    {% for obj in queryset %}
        {{ boj.xxx}}
    {% endfor %}

    <ul class="pagination">
    {{ page_string  }}
    </ul>
"""
from django.utils.safestring import mark_safe


class Pagination(object):
    # 初始化数据
    def __init__(self, request, queryset, page_size=10, page_param="page", plus=5):
        """
        :param request: 请求对象
        :param queryset: 符合条件的数据(根据这个数据给他进行分页处理)
        :param page_size: 每页显示多少条数据
        :param page_param: 在URL中传递的获取页面的参数, 例如: /etty/list/?page=12
        :param plus: 显示当前也的前后几页数据
        """
        import copy
        query_dict = copy.deepcopy(request.GET)
        query_dict._mutable = True
        self.query_dict = query_dict
        self.page_param = page_param

        page = request.GET.get(page_param, "1")
        if page.isdecimal():
            page = int(page)
        else:
            page = 1
        self.page = page

        self.page_size = page_size
        self.start = (page-1) * page_size
        self.end = page * page_size

        self.page_queryset = queryset[self.start:self.end]

        # 数据总条数
        total_count = queryset.count()
        # 总页码
        total_page_count, div = divmod(total_count, page_size)
        if div:
            total_page_count += 1
        self.total_page_count = total_page_count
        self.plus = plus

    def html(self):
        # 计算: 显示当前页的前后5页数据
        if self.total_page_count <= 2 * self.plus + 1:
            # 数据比较少,没有达到11页
            start_page = 1
            end_page = self.total_page_count + 1
        else:
            # 当前页小于5时:
            if self.page <= self.plus:
                start_page = 1
                end_page = 2 * self.plus + 1
            else:
                # 当前页大于5
                if (self.page + self.plus) > self.total_page_count:
                    end_page = self.total_page_count
                    start_page = self.total_page_count - 2 * self.plus
                else:
                    start_page = self.page - self.plus
                    end_page = self.page + self.plus + 1

        # 页码
        page_str_list = []
        # 首页
        self.query_dict.setlist(self.page_param, [1])
        page_str_list.append('<li><a href="?{}">首页</a></li>'.format(self.query_dict.urlencode()))
        # 上一页
        if self.page > 1:
            self.query_dict.setlist(self.page_param, [self.page - 1])
            prev = '<li><a href="?{}">上一页</a></li>'.format(self.query_dict.urlencode())
        else:
            self.query_dict.setlist(self.page_param, [1])
            prev = '<li><a href="?{}">上一页</a></li>'.format(self.query_dict.urlencode())
        page_str_list.append(prev)
        # 页码
        for i in range(start_page, end_page):
            self.query_dict.setlist(self.page_param, [i])
            if i == self.page:
                ele = '<li class="active"><a href="?{}">{}</a></li>'.format(self.query_dict.urlencode(), i)
            else:
                ele = '<li><a href="?{}">{}</a></li>'.format(self.query_dict.urlencode(), i)
            page_str_list.append(ele)

        # 下一页
        if self.page < self.total_page_count:
            self.query_dict.setlist(self.page_param, [self.page + 1])
            prev = '<li><a href="?{}">下一页</a></li>'.format(self.query_dict.urlencode())
        else:
            self.query_dict.setlist(self.page_param, [self.total_page_count])
            prev = '<li><a href="?{}">下一页</a></li>'.format(self.query_dict.urlencode())
        page_str_list.append(prev)

        # 尾页
        self.query_dict.setlist(self.page_param, [self.total_page_count])
        page_str_list.append('<li><a href="?{}">尾页</a></li>'.format(self.query_dict.urlencode()))

        # 跳转页
        search_string = """
                        <li>
                         <form style="float: left;margin-left:-1px" mothod="get">
                             <input name="page" style="position: relative; float: left; display: inline-block; width: 60px; border-radius: 0"
                             type="text" class="form-control" placeholder="页码">
                             <button style="border-radius: 0" class="btn btn-default" type="submit">跳转</button>
                         </form>
                   </li> 
               """

        page_str_list.append(search_string)
        # 转换成安全html代码
        page_string = mark_safe("".join(page_str_list))

        # 返回分页数据页面
        return page_string
